Septic line clogged

I have one commode in my house where the lines are slow to drain. I have a company coming out to pump out my septic tank, but I think I may have another problem. The commode that is slow is "up line" from where it goes in the ground. I have a commode almost directly above where it goes in the ground and is draining alright now. It does make a "gurgling noise" when flush though. I think even after I have the septic tank pumped, I will need something I can pour into the one commode lines that will help clean it out. Any suggestions that will work? I started to get "Rid-X", but have seen on some forums that it is a waste of money. Thanks for any suggestions. The one line that will not drain right is about 25 to 30 ft. from where it goes into the ground. Thanks again..